Perennial ryegrass

About

Perennial ryegrass is what almost every British lawn is mostly made of, and it is there because nothing else takes the wear.

It germinates in a week, establishes faster than any other lawn grass, recovers from being walked on, and repairs itself where the surface is damaged. A family lawn with children, a dog and a football on it stays green because of ryegrass and would not otherwise.

The trade-off is texture. Ryegrass leaves are broader and coarser than the bents and fescues used in fine ornamental turf, so a bowling green or a formal lawn uses very little of it. Modern turf-type cultivars have narrowed that gap considerably and a good one now makes a lawn that looks respectable as well as surviving use.

It is also the backbone of British agriculture. Most of the improved grassland in the country is ryegrass, bred for yield and palatability, and the difference between an agricultural cultivar and a turf cultivar is substantial.

That difference matters when buying seed. A cheap general-purpose mixture may contain agricultural ryegrass, which is coarse, grows fast and needs mowing twice a week.

Appearance and character

A perennial grass forming a dense tuft, reaching 5 cm under regular mowing and 30 to 60 cm if left to flower.

Leaves are narrow, 3 to 6 mm wide, with a distinctly glossy underside and a matt upper surface, and prominent parallel ribs.

The glossy leaf back is the reliable identification, and it separates ryegrass from the duller fescues and meadow grasses at a glance.

Young leaves are folded in the shoot rather than rolled, which is the other identification character used in the seed trade.

The leaf base is often flushed reddish-purple.

Flower spikes appear from May to August, flattened, 10 to 30 cm long, with the spikelets set alternately edge-on directly against the stem in two ranks, giving a zigzag ladder appearance.

It spreads by tillering, producing new shoots from the base of the plant, rather than by runners or rhizomes, so it thickens in place and does not creep sideways.

Turf-type cultivars are finer, darker and slower growing than agricultural cultivars, and they are worth paying for.

Where it is from

Europe, temperate Asia and north Africa, and native throughout Britain and Ireland.

It grows on grassland, roadsides, waysides, waste ground and any reasonably fertile moist soil, and it is one of the commonest plants in the country.

It was the first grass to be deliberately cultivated as a crop in Britain, with records of it being sown as a hay and grazing grass from the seventeenth century.

Ryegrass breeding has been central to British agriculture since the twentieth century, and the Aberystwyth breeding programme produced many of the cultivars still in use.

Turf-type ryegrass breeding is much more recent, largely from the 1970s onwards and largely American, driven by sports pitches and golf.

Italian ryegrass, Lolium multiflorum, is the fast-growing short-lived relative used as a short-term forage crop and sometimes found in cheap seed mixtures, where it is unwelcome because it dies out after a couple of years.

Darnel, Lolium temulentum, is the annual relative of biblical notoriety, which carries a toxic fungal endophyte and was a serious contaminant of grain crops historically. It is now rare in Britain.

How it grows

Sow between mid-March and mid-May or between late August and mid-October, when the soil is warm and moist. September is the best month of the year for a new lawn in Britain.

Prepare the ground thoroughly. Dig or rotavate, remove perennial weeds, level, firm by treading, and rake to a fine tilth. The preparation determines the lawn far more than the seed does.

Sow at 25 to 35 g per square metre for a new lawn, and 15 to 25 g for overseeding.

Rake the seed in lightly and firm it. Do not bury it deeply.

Water in dry weather until it germinates, which takes seven to ten days for ryegrass and longer for the fescues in the mixture.

Keep off it until the first cut, and take that when the grass reaches 5 to 8 cm, cutting back to about 4 cm with sharp blades.

Buy a mixture rather than pure ryegrass for a lawn. A good hard-wearing mixture is around half turf-type ryegrass with strong creeping red fescue and slender creeping red fescue making up the rest, which combines the wear tolerance of one with the fineness and shade tolerance of the other.

Check the cultivar names on the bag. Turf-type ryegrass cultivars are named on any decent product, and a bag that lists only “perennial ryegrass” may contain an agricultural cultivar.

Mow regularly through the growing season, at 2.5 to 4 cm for a family lawn, never removing more than a third of the height at once.

Overseed worn areas in September. Scarify or scratch the surface, sow at 25 g per square metre, rake in and keep moist. Ryegrass establishes fast enough that a worn path across a lawn repairs within six weeks.

Feed twice a year, with a high-nitrogen spring feed in April and a high-potash autumn feed in September.

Scarify and aerate in autumn to remove thatch and relieve compaction.

Through the seasons

Winter ryegrass keeps some colour and grows whenever the soil is above about 5 deg C, which in a mild British winter means the occasional cut.

Spring growth accelerates from March, and this is feeding, sowing and the start of regular mowing.

Summer is peak growth and peak wear, with flowering from May if it is left uncut.

Autumn is the best season for sowing, overseeding, scarifying, aerating and the potash feed.

Care difficulty

Easy. Ryegrass is the most forgiving lawn grass available in Britain.

It germinates fast, establishes quickly, tolerates being walked on, cut short, cut irregularly and neglected, and recovers from damage that kills finer grasses.

The two limitations are shade, where it thins badly, and texture, where it is coarser than a fine ornamental lawn wants.

Diseases are secondary and mostly follow from management. Red thread follows a shortage of nitrogen, and fusarium follows a soft over-fed sward in damp autumn weather.

Watering

Water a new sowing in dry weather until it has germinated and established.

An established lawn needs no watering in Britain in most years. Ryegrass browns off in a drought and recovers completely when the rain returns, which is what it is meant to do.

Soak thoroughly and infrequently if you do water, rather than sprinkling daily, which encourages shallow rooting.

Avoid watering in the evening in autumn, which leaves the sward damp overnight and encourages fusarium.

Aerate compacted ground rather than watering it, since compaction is the commoner reason a lawn struggles in summer.

Warning signs, diseases and pests

Pink or red thread-like growth binding the grass blades together, with patches of bleached straw-coloured turf, is red thread. It follows a shortage of nitrogen and is worst in late summer. Feed the lawn and it grows out.

Small circular patches of yellow-brown turf, sometimes with a white or pinkish fungal growth at the edge in damp weather, is fusarium patch or snow mould. It follows soft over-fed growth in autumn. Avoid nitrogen after August, improve air movement and brush off dew.

Yellow patches that lift like a carpet with no roots underneath, often with birds or badgers tearing at the turf, is leatherjackets or chafer grubs eating the roots. Water the area and cover it overnight with black polythene to bring leatherjackets to the surface, or apply a biological nematode treatment in late summer.

Thin sparse growth under trees or beside a north wall is shade. Ryegrass has poor shade tolerance. Overseed with a shade mixture based on fescues, or accept that grass is the wrong answer there.

A spongy surface that holds water is thatch. Scarify in autumn.

Compacted worn tracks are physical damage. Aerate, overseed in September, and consider a path where people walk.

Coarse fast-growing patches in a fine lawn is agricultural ryegrass from a cheap seed mixture. Dig it out and overseed with a turf-type cultivar.

Moss is a symptom rather than a cause, and it follows shade, compaction, poor drainage or mowing too short.

Growing environment

Full sun to light shade. It thins badly in real shade, where fescues do better.

Any reasonable soil, and it prefers moist fertile ground. It tolerates clay well and dries out on thin sand.

Fully hardy and it grows through mild winters.

Sow at 25 to 35 g per square metre for a new lawn and 15 to 25 g for overseeding.

It suits a family lawn, a play area, a dog run, a sports pitch, a path across grass, a verge or any area that gets walked on.

It does not suit a fine ornamental lawn, deep shade or a wildflower meadow, where its vigour outcompetes the flowers.

Use a mixture rather than pure ryegrass for a garden lawn, combining turf-type ryegrass for wear with creeping red fescue for fineness and shade tolerance.

Its wildlife value in a mown lawn is low, which is a fair criticism of a ryegrass lawn. Leaving an area unmown, or overseeding a rough area with a meadow mixture, does far more for insects than anything else you can do to a lawn.

Feeding

Feed twice a year for a lawn in ordinary use.

Apply a high-nitrogen spring and summer feed in April, which drives the growth and colour.

Apply a high-potash autumn feed in September, which hardens the sward for winter and reduces disease.

Do not apply nitrogen after August. Soft growth going into a damp autumn is what fusarium patch feeds on.

Leave the clippings on with a mulching mower in dry weather, which returns nitrogen and reduces the need to feed.

Red thread appearing in late summer is a sign the lawn is short of nitrogen rather than diseased in any serious sense.

Troubleshooting

When should I sow a new lawn? September is the best month in Britain, with mid-March to mid-May as the alternative. Warm moist soil and less competition from weeds are what make autumn better.

How do I repair a worn patch? Overseed in September. Scratch or scarify the surface, sow at 25 g per square metre, rake in and keep it moist. Ryegrass germinates in a week and a worn path repairs within six weeks.

Which seed mixture should I buy? For a family lawn, one based on turf-type perennial ryegrass with creeping red fescue. Check that the cultivars are named on the bag, since a product listing only “perennial ryegrass” may contain a coarse agricultural cultivar.

Why is my lawn thin under the tree? Ryegrass has poor shade tolerance. Overseed with a fescue-based shade mixture, or accept that grass is the wrong plant for that spot and use ground cover instead.

There are pink threads in the grass and pale patches. Red thread, which follows a shortage of nitrogen. Feed the lawn and it grows out.

The turf lifts up like a carpet with no roots. Leatherjackets or chafer grubs eating the roots. Apply a biological nematode treatment in late summer, and expect birds and badgers to make the damage worse while looking for them.

How short should I mow it? Two and a half to four centimetres for a family lawn, and never remove more than a third of the height in one cut. Mowing shorter than that encourages moss and weakens the grass.

Why does it go brown every summer? Drought dormancy, which is normal and reversible. Ryegrass browns off and recovers completely when the rain returns. Watering a lawn through a British summer is rarely necessary.

Can I use it in a wildflower meadow? No. Ryegrass is too vigorous and outcompetes the flowers. Meadow mixtures use fine slow grasses such as crested dogstail and sheep’s fescue.